Time delay fuse

ABSTRACT

A time delay fuse has a ball rotor carrying the detonator charge in a bore along the axis of mass symmetry, and normally held safe, out of line by a detent clip. Release of the clip requires both adequate set back force and centrifugal force. Once the rotor has rotated into the armed, in-line disposition, it is interlocked in this disposition.

United States Patent Richard T. Ziemba Burlington, Vt.

Appl. No. 804,443

Filed Mar. 5, 1969 Patented Sept. 28, 1971 Assignee General Electric Company Inventor TIME DELAY FUSE 5 Claims, 5 Drawing Figs.

U.S. Cl 102/79, 102/82,102/7l Int. Cl F42c 9/02, F42c 7/00, F42c 9/00 Field of Search 102/79, 82, 71

[56] References Cited UNITED STATES PATENTS 2,715,873 8/1955 Thompson 102/79 X 3,397,640 8/1968 Ziemba et a1 102/79 X Primary Examiner-Benjamin A. Borehelt Assistant Examiner-Thomas H. Webb Attorneys-Bailin L. Kuch, lrving M. Freedman, Harry C.

Burgess, Frank L. Neuhauser, Oscar B. Waddell and Melvin M. Goldenberg ABSTRACT: A time delay fuse has a ball rotor carrying the detonator charge in a bore along the axis of mass symmetry, and normally held safe, out of line by a detent clip. Release of the clip requires both adequate set back force and centrifugal force. Once the rotor has rotated into the armed, in-line disposition, it is interlocked in this disposition.

TIME DELAY FUSE BACKGROUND OF THE INVENTION l. Field ofthe Invention This invention is related to time delayed fuses for ammunition of relatively small calibre, and especially to devices for maintaining the safe or the armed status of the fuse.

2. Prior Art The fuse of this invention is an is an improvement on the fuse shown in my earlier U.S. Pat. No. 3,397,640, issued Aug. 20, I968. In that patent I disclosed a fuse which has a ball rotor supporting and normally disposing a detonator out of alignment with the firing pin and the booster charge, and disposing the detonator in alignment with the firing pin and the booster charge after the application over a predetermined period of time of a predetermined centrifugal force. Specifically, the rotor is held in an out-of-line position by means of a rotor detent spring. This spring locks the rotor in an out-ofline position until projectile spin is sufficient to cause the spring to open, thereby releasing the rotor. Once the rotor is free of the spring, it is free to rotate, due to its dynamic mass unbalance, to an in-line position. Since the diameter of the detonator within the rotor is usually relatively large, the difference in the moments between the principal axes of the rotor is large and, therefore, the driving torque is high. Thus, the rotor aligns itself in a very few milliseconds once the projectile emerges from the gun muzzle. Accordingly, it is an object of this invention to reduce the driving torque to increase the time delay to alignment. Another object of this invention is to precondition arming on the simultaneous presence of both adequate spin and setback forces.

For normal target impact conditions, the firing pin is driven into the detonator to provide fuse function, i.e., initiation. However, at low target impact angles, the projectile and the fuse fixed thereon tend to rotate relative to the ball detonator, and, thereby, cause a misalignment between the firing pin and the detonator. This occurs because the ball rotor cannot change its alignment fast enough to follow the shift of the fuse at the time of target impact. A gross misalignment will result in a failure of fuse function. Therefore, another object of this invcntion is to lock the ball rotor into alignment with the firing SUMMARY OF THE INVENTION A feature of this invention is a time delay fuse for a projectile including a ball rotor journaled for rotation within a cavity in the fuse. The firing pin, said cavity and the booster charge lie along the longitudinal axis of the fuse. The rotor carries a detonator in a diametral bore, and a retaining ring mounted on a set out into the ball normally fixes the ball with the detonator out of alignment with the longitudinal axis of the fuse. To release the rotor, the ring must be moved aft by setback force and must be enlarged by centrifugal force. After the rotor has rotated into alignment with the longitudinal axis, it is locked into alignment by mating surfaces on the ball and the cavity.

BRIEF DESCRIPTION OF THE DRAWING These and other objects, advantages and features of this invention will be apparent from the following specification thereof taken in conjunction with the accompanying drawing in which:

FIG. I is a longitudinal cross section of the prior art fuse, substantially as shown in U.S. Pat. No. 3,397,640;

FIG. 2 is a longitudinal cross section of one aspect of the present invention, showing an improved low mass ball rotor assembly, providing a relatively long time delay to arm, compared to the fuse of FIG. 1;

FIG. 3 is a longitudinal cross section of another aspect of the present invention, showing an improved ball rotor assembly requiring both setback and centrifugal forces to arm;

FIG. 4 is a longitudinal cross section of another aspect of the present invention, showing an improved ball rotor assembly having a surface to mate with the cavity to block the ball in the armed disposition and FIG. 5 is a view similar to FIG. 4 showing the ball rotor assembly locked in the armed disposition.

DESCRIPTIONS OF THE EMBODIMENTS The prior art fuse is shown in FIG. 1 to include a fuse body 10 of substantially conical shape. The body has a longitudinal bore having an aft portion 12 or relatively large diameter terminating in a medial subportion 14 of hemispherical shape, and a forward position 16 of relatively small diameter. The aft bore portion is internally threaded to receive a booster housing 18 having a central cavity 20 containing a booster charge 22. A firing pin assembly 24, which may be of the self-destruct type shown in U.S. Pat. No. 3,397,640 supra, is disposed in the forward bore portion, and covered by a nose cap 26. The forward end 28 of the booster housing 18 has a semispherical recess therein, so that, in conjunction with the fuse body bore a medial subportion 14, a substantially spherical cavity is formed when the booster housing is screwed into the fuze housing. A ball rotor 30 is disposed within the spherical cavity 28/14. The ball has a fore flat 32 subtending a diametral bore 34 in which is captured a detonator cartridge 36. A horseshoeshaped groove 38 is cut into the surface of the ball and receives a horseshoe-shaped retaining clip 40. An internal, annular groove 42 is cut into the fuze housing bore adjacent the fore end of the detonator housing. In use, the ball rotor is held with the detonator in the out of line, safe, disposition. As the projectile is fired through the tube of the weapon it is spun by the rifling in the tube. The clip 40 locks the rotor in the out of line disposition shown in FIG. I until the rotor assembly spin is sufficient to cause the clip to expand into the groove 42, thereby releasing the ball rotor. Once the ball rotor is free of the spring, it is free to rotate, due to dynamic mass unbalance to an in-line, armed disposition. Since the diameter of the detonator within the rotor is larger, the difference in the mo ments between the principal axes of the rotor is large and, therefore, the driving torque is high. Thus, the rotor aligns itself in a very few milliseconds after the projectile emerges from the tube of the weapon.

The conditions which govern the arming delay in a ball rotor fuze mechanism are the following:

1. Spin rate of the projectile;

2. Difference in the moments of inertia of the rotor's principal axes;

3. Initial angular displacement of the detonator relative to the flight axis of the projectile;

4. Mass of the rotating parts; and

5. Coefficient of friction between the rotor and the cavity surfaces.

To increase the arming delay by reducing the mass of the rotating parts, the ball rotor has been modified as shown in FIG. 2, inter alia, by changing the horseshoe-shape groove 38 to a circular cut 238 around the entire perimeter of the ball. The horseshoe-shaped clip 40 is retained. The circular cut allows the ball rotor to spin independently of the retaining clip, therefore, more slowly, during its travel through the tube of the weapon.

The prior art fuze requires only adequate spin to shift from its safe to armed disposition. The possibility of an inadvertant arming of the fuse is further minimized by requiring both adequate spin and adequate setback simultaneously to shift the fuse from its safe to armed disposition, as shown in FIG. 3. The annular groove in the fuse housing has been narrowed and has been located relatively aft, adjacent to the fore end of the booster housing, and is here shown as an annular groove 342. The horseshoe-shaped groove in the ball rotor has been changed to an annular groove 338 around the entire perimeter of the ball. The horseshoershaped clip 40 is retained. The bottom of the groove 338, however, is not cylindrical but rather is conical, to hold the clip 40 forward, out of transverse alignment with the groove 342. An additional annular groove 339, contiguous to groove 342, is provided to accommodate the clip 40 in its forward disposition. The ball retaining clip 40 can no longer open directly into the groove 342. Projectile set back force is required to move the clip aft, up the cone, adjacent the booster housing fuse end, to be in transverse alignment with the groove 342. If the set back force is present, but sufficient spin is not present to open the clip, the ball rotor will remain locked in its out-of-line, safe, disposition. lf sufficient spin is present, but sufficient set back force is not present, the clip will not be able to open because it will not be aligned with the groove 342.

To insure that once armed, the fuse remains armed, the ball rotor has been modified, as shown in FIGS. 4 and 5, to lock the ball to the housing after alignment. A mating flat chordal surface 400 is formed in the hemispherical bore portion of the fuse housing to mate with the fore flat 32 on the ball rotor. During arming, the ball rotor rotates into alignment with the firing pin 24 until the flat 32 mates with the seat flat 400. At this point, the forward creep effect developed by rotation of the ball rotor will hold the parts together. At target impact, the deceleration of the projectile will provide an additional locking force between the rotor and the housing to preclude misalignment between the detonator cartridge and the firing pin. Thus, low angle target entries are possible without the probability of fuse function failure.

Although they have been illustrated separately, it will be obvious that the cone shaped groove 338 on the ball rotor, with the aft mating groove 342 in the housing, may be combined with the flat 32 on the ball rotor, with the mating flat 400 in the housing, in a single fuse which requires both adequate setback force and spin to arm, but which once armed, remains armed.

It may be noted that while the diameter of the rotor has been illustrated as almost equal to the transverse diameter of the cavity, it may be made significantly smaller to allow a volume for coupling material, such as a layer of silicone.

What is claimed is:

1. A time delay fuse mechanism having a safed disposition and an armed disposition, for ammunition, comprising:

a housing having a longitudinal axis extending fore and aft,

and a substantially spherical cavity therein which is symmetrical about said axis;

a substantially spherical rotor disposed in said cavity having an axis of mass symmetry and a diametral bore coaxial therewith and adapted to receive a detonating charge therein;

a first annular groove formed into the periphery of said rotor perpendicular to a first diameter which is angularly displaced from said axis of mass symmetry and which first diameter, in the safed disposition is coaxial with said housing longitudinal axis, said groove defining a cone having a portion of relatively, smaller diameter proximate to the center of said rotor and a portion of relatively larger diameter remote from said center of said rotor;

a second annular groove formed into the wall of said housing cavity perpendicular to said housing longitudinal axis and adjacent to said cone portion of relatively larger diameter;

a third annular groove formed into the wall of said housing cavity perpendicular to said housing longitudinal axis, ad-

jacent to said cone portion of relatively smaller diameter, and contiguous to and of smaller diameter than said second annular groove;

and an expansible element, normally disposed on and embracing said cone portion of relatively smaller diameter, and extending at least in part into said third annular groove thereby precluding rotation of said rotor in said cavity;

said expansible element adapted, upon the application of an adequate setback force, to ride aft along said longitudinal axis from the disposition normal disposition adjacent said third annular groove to an intermediate disposition adjacent said second annular groove, and when in said intermediate disposition, upon the application of an adequate centrifugal force, to expand into said second annular groove to free said rotor for rotation within said cavity into the armed disposition. I I 2. A time delay fuse mechanism, having a safed disposition and an armed disposition, for ammunition, comprising;

a housing having a longitudinal axis extending fore and aft,

and a cavity therein which is symmetrical about said axis;

a substantially spherical rotor disposed in said cavity having an axis of mass symmetry and a diametral bore coaxial therewith and adapted to receive a detonating charge therein, and a first diameter which is angularly displaced from said axis of mass symmetry;

spin releasable interlocking means disposed in part in said rotor and in part in said cavity for normally retaining said rotor with said first diameter coaxial with said longitudinal axis, and adapted, under adequate centrifugal force to release said rotor for rotation in said cavity to the armed disposition with said axis of mass symmetry coaxial with said longitudinal axis;

additional interlocking means disposed in part on said rotor and in part on a surface of said cavity for retaining said rotor, upon rotation into said armed disposition, in said armed disposition.

3. A fuse according to claim 2, wherein:

said cavity has a forward portion of substantially hemispherical shape, with a chordal flat surface perpendicular to said longitudinal axis; and

said rotor has a mating chordal flat surface perpendicular to said axis of mass symmetry; said flat surfaces serving as said additional interlocking means.

4. A fuse according to claim 1, further including:

interlocking means disposed in part on said rotor and in part cavity for retaining said rotor, upon rotation into said armed disposition, in said armed disposition.

5. A fuse according to claim 4, wherein:

said cavity has a forward portion of substantially hemispherical shape, with a chordal flat surface perpendicular to said longitudinal axis; and

said rotor has a mating chordal flat surface perpendicular to said axis of mass symmetry;

said flat surfaces serving as said additional interlocking means. 

1. A time delay fuse mechanism having a safed disposition and an armed disposition, for ammunition, comprising: a housing having a longitudinal axis extending fore and aft, and a substantially spherical cavity therein which is symmetrical about said axis; a substantially spherical rotor disposed in said cavity having an axis of mass symmetry and a diametral bore coaxial therewith and adapted to receive a detonating charge therein; a first annular groove formed into the periphery of said rotor perpendicular to a first diameter which is angularly displaced from said axis of mass symmetry and which first diameter, in the safed disposition is coaxial with said housing longitudinal axis, said groove defining a cone having a portion of relatively smaller diameter proximate to the center of said rotor and a portion of relatively larger diameter remote from said center of Said rotor; a second annular groove formed into the wall of said housing cavity perpendicular to said housing longitudinal axis and adjacent to said cone portion of relatively larger diameter; a third annular groove formed into the wall of said housing cavity perpendicular to said housing longitudinal axis, adjacent to said cone portion of relatively smaller diameter, and contiguous to and of smaller diameter than said second annular groove; and an expansible element, normally disposed on and embracing said cone portion of relatively smaller diameter, and extending at least in part into said third annular groove thereby precluding rotation of said rotor in said cavity; said expansible element adapted, upon the application of an adequate setback force, to ride aft along said longitudinal axis from the normal disposition adjacent said third annular groove to an intermediate disposition adjacent said second annular groove, and when in said intermediate disposition, upon the application of an adequate centrifugal force, to expand into said second annular groove to free said rotor for rotation within said cavity into the armed disposition.
 2. A time delay fuse mechanism, having a safed disposition and an armed disposition, for ammunition, comprising; a housing having a longitudinal axis extending fore and aft, and a cavity therein which is symmetrical about said axis; a substantially spherical rotor disposed in said cavity having an axis of mass symmetry and a diametral bore coaxial therewith and adapted to receive a detonating charge therein, and a first diameter which is angularly displaced from said axis of mass symmetry; spin releasable interlocking means disposed in part in said rotor and in part in said cavity for normally retaining said rotor with said first diameter coaxial with said longitudinal axis, and adapted, under adequate centrifugal force to release said rotor for rotation in said cavity to the armed disposition with said axis of mass symmetry coaxial with said longitudinal axis; additional interlocking means disposed in part on said rotor and in part on a surface of said cavity for retaining said rotor, upon rotation into said armed disposition, in said armed disposition.
 3. A fuse according to claim 2, wherein: said cavity has a forward portion of substantially hemispherical shape, with a chordal flat surface perpendicular to said longitudinal axis; and said rotor has a mating chordal flat surface perpendicular to said axis of mass symmetry; said flat surfaces serving as said additional interlocking means.
 4. A fuse according to claim 1, further including: interlocking means disposed in part on said rotor and in on a surface of said cavity for retaining said rotor, upon rotation into said armed disposition, in said armed disposition.
 5. A fuse according to claim 4, wherein: said cavity has a forward portion of substantially hemispherical shape, with a chordal flat surface perpendicular to said longitudinal axis; and said rotor has a mating chordal flat surface perpendicular to said axis of mass symmetry; said flat surfaces serving as said additional interlocking means. 